Monday, March 3, 2014

Final repairs on MFJ loop

Time to repair the control box.
It seems that almost all the bugs have been ironed out with the MFJ 1788 loop antenna. I sure have had an adventure with the unit but things seem to be on the upswing now. Some of the indicators the MFJ loop gives you when your match is good are High noise level meaning you are in the ball park. The SWR meters on the control box that visually tell you the SWR is good. Finally there is a tone that comes from within the control box when you are auto tuning the loop. As far as I am concerned this tone is only within the range of our cat Oliver's hearing. day when I was tuning the loop in auto mode and all was going well until Julie tapped me on the headphones saying "can you not hear that ANNOYING sound!! I took my headphones off and still nothing it was not until I put my ear right up to the MFJ control box could I hear the tone. WOW my hearing must be way off  as Julie said it was very noticeable to her in the living room and to add insult to injury she also heard it over the TV. Needless to say this event happened a few more times and
Ready to remove switch
it seemed apparent that it was time to cut the wires to this speaker. While I was in there I also had to replace a switch that controls the range of the watt meter on the MFJ control head. The original switch did not work very well at all and MFJ was kind enough to send me 3 extra ones. Cutting the wires to the speaker (I could never hear) was very fast and easy but for this switch to be changed most of the unit would have to be taken apart it seemed. Once I was ready to remove the old switch and replace it with the new one it was very easy........having said "easy" it means that with the right tools it was easy. I used the Hakko 808 de-soldering gun and believe me this unit makes very easy work of removing the old solder. To the point were the defective switch just falls out of the board. In the past I have used the hand held de-soldering pumps and the wicks as well but nothing works as well as this unit. The solder station I have is the Weller WES 51 and it has served me well for many years and you can change out the tips for various jobs you want to do. So with the wires cut to the speaker and the new switch installed it's now time to just operate and no more (I hope) fooling around with the antenna.
A great tool to have


  1. Hello Mike, it's a bad thing MFJ uses bad quality switches but hey it's great service they send you a few new ones. The hakko tool is a great thing to have. I can't see how it works exactly but I pressume the tip has a hole in it and the tool sucks the solder inside? Much better as wicks or a pump. 73, Bas

  2. Good morning Bas, yes the Hakko unit is like a hand held vacuum for solder. It removes the solder completely from the pad and in most cases the defective device falls out of the board.


  3. This article is very helpful thank you very much for sharing

  4. Hi Mike, sorry to say, but MFJ sucks. I read too many times this kind of stories about MFJ. They must be ashamed. I hope that your problems are solved now. 73 Paul